Hi all:
It has been a few years (1980's or so) since I did this, but here is another idea:
Another possible source of discharge papers: Try the County clerk's Office on the county of residence of the soldier AT THE TIME OF THE WAR.
After the war, States often paid a bonus to any veteran who filed his/her discharge with the County of Residence. Many counties still hold these records. Sometimes there is a charge of a few dollars for a copy.
Some States hold these records in the State Capitol; A few States limit access to these records to next of Kin. If I remember correctly, Illinois does this.
Incidentally, as part of my Ph.D thesis research, I obtained some 195 discharge records this way. I started out with an old address book one veteran had kept and went from there. Tedious, but this was before days of the internet and White Pages etc.